Methods of administering test substance

Among the various techniques for administering the test drug in an in vivo study are the following  

Incorporating the test substance into the diet, which is then administered to the subject. This procedure may be especially relevant to the analysis of the absorption of drugs that are contaminants of the diet. 

Intubating the test substance into the stomach, a procedure that allows more precise control of the total dose administered. 

With both of the above methods the rate and possibly the extent of absorption of the test substance may be markedly affected by the gastric emptying pattern of the subject. 

Directly administering the test substance into the intestinal lumen, which eliminates the influence of gastric emptying. In human studies, substances can be administered through small-bore intubating 

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